<?php
/**
 * Created by PhpStorm.
 * User: zhangrongxiang
 * Date: 2017/3/10
 * Time: 下午5:29
 */

$str = '';
$int = 0;

$arr = [];

$null = null;//不存在

if ($str){
    echo 'str';
}
if (empty($str)){
    echo "empty";
}

if (isset($str)){
    echo "isset";
}

if (!$null){
    echo "null";
}
if (empty($null)){
    echo "empty";
}
if (isset($null)){
    echo "null";
}

